Fibrous glass insulation products generally comprise matted glass fibers bonded together by a cured thermoset polymeric material. Molten streams of glass are drawn into fibers of random lengths and blown into a forming chamber where they are randomly deposited as a mat onto a traveling conveyor. The fibers, while in transit in the forming chamber and while still hot from the drawing operation, are sprayed with an aqueous binder. A phenol-formaldehyde binder is currently used throughout the fibrous glass insulation industry. The residual heat from the glass fibers and the flow of air through the fibrous mat during the forming operation are generally sufficient to volatilize a majority all of the water from the binder, thereby leaving the remaining components of the binder on the fibers as a viscous or semi-viscous high-solids liquid. The coated fibrous mat, which is formed in a compressed state due to the tremendous flow of air through the mat in the forming chamber, is then transferred out of the forming chamber to a transfer zone where the mat vertically expands due to the resiliency of the glass fibers. This vertical expansion is extremely important to the successful manufacture of commercially acceptable fibrous glass thermal or acoustical insulation products. Thereafter, the coated mat is transferred to a curing oven where heated air is blown through the mat to cure the binder and rigidly bond the glass fibers together.
Phenol-formaldehyde binders are widely used because they have a low viscosity in the uncured state, yet form a rigid thermoset polymeric matrix for the glass fibers when cured. A low binder viscosity in the uncured state is required to allow the maximum vertical expansion of the coated mat when it exits the forming chamber. A binder which forms a rigid matrix when cured is required so that a finished fibrous glass thermal or acoustical insulation product, when compressed for packaging and shipping, will recover to its as-made vertical dimension when installed in a building.
Insulation manufacturers have long desired an alternative polymeric binder system for fibrous glass products. However, low molecular weight, low viscosity binders which allow maximum vertical expansion of the mat in the transfer zone generally cure to form a non-rigid plastic matrix in the finished product, thereby reducing the attainable vertical height recovery of the finished insulation product when installed. Conversely, high viscosity binders which generally cure to form a rigid matrix in the finished product do not allow maximum vertical expansion of the coated, uncured mat.
U.S. Pat. No. 4,076,917 to Swift et al. discloses the use of .beta.-hydroxyalkylamides to cure polycarboxy polymers such as acrylic acid. Such a system, however, is too viscous for use as a fibrous glass binder.
It would be desirable to prepare a non-phenol formaldehyde binder having a low viscosity when uncured and structural rigidity when cured.